Manufacture of ring gear and other ring blanks

ABSTRACT

Method of an apparatus for cold pressing metal ring blanks for ring gears, piston rings and other products from stock of circular form in cross section, so as to change its crosssectional shape into substantially barrellike formation and to also form the stock into a ring, subsequently subjecting the ring blank to a second cold pressing operation in a circular chamber of channel or rectangular shape in cross section, whereby molecular flow of the metal is facilitated until it has passed its yield point without the pressed blank filling said chamber.

Waited mates Watent Stem et a1.

1451 3am. NAME [72] lnventors: Lionel Stern,

1541 MANUFAQ'ITURIE (NF REM GEAR AND OTHER RHNG BLANKS Kew; Bernard Milton lilladaway, Highett, both of Australia A. T. Richardson & Sons Proprietary Limited, Melbourne, Victoria, Australia 221 Filed: Sept. 12,1969

21 Appl.No.: 857,332

[73] Assignee:

[30] Foreign Application Priority Data Sept. 26, 1968 Australia ..43,915/68 52 new ..72/130,72/132,29/8 51 1111.011. ..B2l1l1ll/00,B2ilpl3/00 5s Fieldofsearclh ..72/130,366,368,}l32g48;

[56] References Cited UNITED STATES PATENTS l,851,785 3/1932 7 Taylor 12/122 2,206,068 7/1940 Yoder ..72/132 2,229,639 1/1941 C0rnell.. ..72/368 3,036,622 5/1962 l'litz ..72/366 3,042,100 7/1962 Norton ..72/130 Primary Examiner-Richard J. l-lerbst Assistant ExaminerR. M. Rogers Attorney-Diller, Brown, Ramik 8: Holt [5 7] ABSTRACT A Method of an apparatus for cold pressing metal ring blanks for ring gears, piston rings and other products from stock of circular form in cross section, so as to change its cross-sectional shape into substantially barrellike formation and to also form the stock into a ring, subsequently subjecting the ring blank to a second cold pressing operation in a circular chamber of channel or rectangular shape in cross section, whereby molecular flow of the metal is facilitated until it has passed its yield point without the pressed blank filling said chamber.

11 Claims, 10 Drawing Figures PATENIED JAN 1 a me g a 12 a SHEET 1 or 3 L! ON BERN /N TURS ST N (PK HILTON MONDAY ATTOIZMEYS MANUFACTURE OF RING GEAR AND OTHER RING BLANKS This invention relates to the manufacture by a cold pressing method of metal ring blanks of the kind which are particularly suitable for the subsequent manufacture of ring gears, piston rings and other products in which the inside or outside, or both diameters of the ring are of critical importance for subsequent fitting.

According to existing trade practice of producing ring gear blanks in which no machining is required prior to the teethhobbing operation, each ring is formed from straight metal stock of rectangular shape in cross section which is coiled to the desired diameter usually by a conventional three-roller coiling machine, after which the coil is cut into predetermined lengths and the abutting ends of the rings are welded together.

It is desirable to set the ring to its final dimensions by compressing the metal beyond its yield point while being dimensionally restrained. In the case of a ring gear, this is achieved by making the basic ring of slightly smaller internal diameter than that of the finished product and subjecting its opposite side faces to a cold pressing operation between opposed platens after the internal diameter of the ring has been slightly increased and rounded by passing a sizing mandrel therethrough.

When a rectangular sectioned basic ring is employed, it has been found in practice that optimum dimensional stability and uniformity is not achieved by the aforesaid pressing operations unless abnormally high pressures are used. The latter tend to cause breakagein the pressing tooling and also the formation of undesirable fins or burrs on the blank where the metal is forced between the mandrel working face and the adjacent circular faces of the platens. In the case of a ring gear such burrs are formed at the opposite edges of the inner periphery of the ring.

When a ring gear, for example, is formed from rectangular sectioned stock as aforesaid, the basic ring blank substantially fills the three sided or channel-shaped chamber formed by the sizing mandrel and the opposed platens before pressing and is necessarily firmly held or locked up by frictional restraint between the opposed faces of the platens, while the pressing action is taking place. The locking action on the basic ring within the confinement of such a die chamber during pressing restricts the opportunity for the entire ring section to flow and yield and take the desired permanent set.

The primary object of the present invention is to provide an improved basic ring blank having such a predetermined crosssectional shape that when subjected to cold pressing within a three-sided chamber as aforesaid, the undesirable locked up" condition that occurs when basic rings of rectangular cross section are employed, is avoided, or at least reduced to a minimum. Substantially all of the basic ring section is compressed and flows beyond its yield point with the application of minimum force to achieve the desired diametral and flatness stability and uniformity in the finished product.

Another object is to provide an improved method of and machine for manufacturing the improved ring blanks by a cold pressing operation.

One of the important features of the invention concerns a method of forming a metal ring blank of the kind indicated from wire or bar stock of circular form in cross section which comprises cold pressing the stock so as to change its original cross-sectional shape into substantially barrellike formation with opposed flat surfaces and intervening surfaces of convex curvature in cross section, curving said stock into substantially ringlike formation and subsequently subjecting the ring blank of barrellike cross section to a second cold pressing operation within a circular chamber of predetermined shape in cross section, whereby molecule flow within the ring blank during such second pressing operation is facilitated until substantially all of the metal in said blank has passed its yield point and set, without the pressed blank filling said chamber.

Another feature concerns apparatus for use in carrying out the aforesaid method, the apparatus comprising a pair of opposed presser rollers having means for driving at least one of said rollers, means for directing the leading end of the wire stock of circular cross section between said presser rollers and guide means located at that side of the presser rollers remote from said directing means, so as automatically to direct the leading end portion of the flattened wire stock as it emerges from between said presser rollers into a curved path of predetermined diameter and means for cutting the flattened wire into predetermined lengths suitable for forming a ring blank of the desired size.

Referring to the drawings which form part of this specification:

FIG. 1 is a sectional perspective view of the original wire or bar stock employed and which is initially of circular form in cross section,

FIG. 2 is a fragmentary sectional elevation of pressing apparatus employed in completing the manufacture of the new product. In this case the stock is being pressed in a circular chamber of channel shape in cross section and the internal diameter of the finished product is critical, but the external diameter is not,

FIG. 3 shows the parts seen in FIG. 2 at the completion of the pressing operation,

FIG. 3a is an enlargement of FIG. 3.

FIG. 4 is a view similar to FIG. 2 in accordance with a modification in which a circular chamber of substantially rectangular form in cross section is employed. In this case both the internal and external diameters of the finished .product are critical,

FIG. 5 is another view of the parts seen in FIG. 4, but at the completion of the pressing operation,

FIG. 6 is a view similar to FIG. 2, with the exception that provision is made for sizing the external diameter of the finished product, while its internal diameter is not critical,

FIG. 7 is a view similar to FIG. 6, but in which provision is made for finishing a product in which both the internal and external diameters are critical,

FIG. 8 is a part sectional end elevation of apparatus for use in carrying out the improved method and showing the original -bar stock of circular form in cross section being flattened into the desired barrellike cross section and at the same time being curved into substantially ringlike formation; and

FIG. 9 is a part sectional side elevation of the apparatus seen in FIG. 8.

In accordance with the present invention, the basic ring blank is formed from wire or bar stock 2 of circular form in cross section. This stock is initially flattened on opposite sides to change the sectional shape to substantially barrellike formation 3 having substantially flat and parallel faces at opposite sides of the stock and convex faces on the remaining opposite sides, as seen in FIGS. 2 and 4.

After this initial treatment, the stock is cut to predetermined length after having been coiled so that the opposite ends may be secured together by welding. As usual, the basic ring blank so formed has an internal diameter slightly smaller than the finished product in the case of a ring gear or like blank where the internal diameter is critical.

When the improved basic ring blank is subjected to cold pressing in a circular three-sided die chamber 4 as aforesaid and which is formed by the opposed platens 6 and 7 and the sizing mandrel 8 as seen in FIGS. 2 and 3, the barrellike cross section 3 of the ring enables desirable flow of the metal to occur at, or adjacent to the four comers of the ring section without the chamber becoming entirely filled. Furthermore, during this pressing operation substantially all of the ring section has yielded and set before any undesirable frictional locking forces can act on the ring, whereby a most accurate and stable ring of predetermined thickness is produced. In the case of a ring gear the internal diameter of the ring is most accurate, and although the opposite or outer face 9 of the ring is of slightly convex formation, this is no disadvantage in that the teeth are subsequently formed in this part of the ring.

In some cases however, the outside as well as the inside diameter of the ring is of critical importance. This requirement however, does not present any difficulty and may be readily achieved by forming one of the platens 7a with a rightangled shoulder 11 so as to form a closed pressing chamber 12 of rectangular form when the platens and mandrel are operatively positioned, as seen in FIG. 5. In this case, desirable metal flow at the corner portions of the ring blank are obtained and the required sizing of the internal and external diameters of the ring achieved without the use of abnormally high pressures or the formation of objectionable burrs or the like on the finished product.

It will be obvious that the invention is not restricted to the formation of ring gear blanks, but that the same technique may be employed in the manufacture of ring blanks for a wide variety of other purposes. For example, split piston rings may be readily produced by the same method of manufacture from wire stock stock material 2 originally of circular from in cross section.

In this case, the external diameter of the piston ring is necessarily of critical importance and consequently the ring may be sized by passing a sizing ring 13 over a basic split ring blank, after which it is conditioned by pressing between opposed platens 6 and 7 as in FIG. 6 or any other suitable pressure members. The internal diameter of the piston ring need not be of critical importance and furthermore, it is of course unnecessary to weld the opposite ends of the ring together.

If desired, the same type of pressing apparatus may be modified so as to produce a-finished product of the same type as that shown in FIG. in which both the internal and external diameters of the product are critical. Such a modified pressing apparatus is shown in FIG. 7 and it will be noted that one of the platens 6 or 7 is provided with a stepped shoulder 11a so as to form a circular pressing chamber of rectangular form in cross section.

The invention also provides simple and inexpensive apparatus for use in the manufacture of the improved ring blanks. As seen in FIGS. 8 and 9, this apparatus includes a pair of opposed pressure rollers 14 and 16 having driving means for at least one of them and any suitable means for varying the spacing between the rollers in accordance with requirements.

The apparatus also includes a reel, not shown, or any other suitable support for a coil of circular sectioned wire 2 from which the ring blanks are to be formed, and means for directing the leading end of the wire between the two presser rollers 14 and 16. One of these is preferably larger than the other in order to facilitate the initial feeding of the wire between the rollers.

Such wire directing means may include a guide tube 15 and/or a pair of feed rollers located in advance of the presser rollers and having grooved peripheries facing each other so as to accommodate the wire therebetween. This pair of rollers is preferably mounted upon a support which is movable transversely of the wire axis at substantially right angles to the parallel axes of the presser rollers 14 and 16 when viewed from the side thereof.

Such movement of the roller support in either direction is adapted to vary the angle at which the wire is fed between the presser rollers 14 and 16 and thereby determines whether the width of the flat surface formed, for example, on the inside of the basic ring blank is the same, greater or less than the width of the flat surface formed on the outside of the ring blank in accordance with requirements.

Associated with the foregoing, is guide means for automatically directing the leading end of the wire as it emerges from between the presser rollers 14 and 16 into a curved path of predetermined diameter. Such guide means may consist of a rotatable roller 17 which is preferably of smaller diameter than the presser rollers and located at that side thereof remote from the wire-directing means. This rotatable guide roller is also preferably carried by an adjustable mounting so that its operative position in relation to the nip zone between the presser rollers may be varied so as to determine the diameter ofthc ring blank being formed.

Alternatively, a fixed guide member or shoe 18 may be employed instead of the rotatable guide roller.

During the passage of the wire between the pair of presser rollers 16 and 17 for flattening the opposite sides of the wire, the compression to which the wire is subjected causes its metal to yield to such a degree that very accurate coiling is obtainable without undesirable springback. It will be appreciated that coiling of the wire is initiated in the yielding metal at the nip zone between the presser rollers and controlled by locating the associated rotatable guide roller 17 or other guide member 18 in the desired operative position.

Each of the presser rollers may be mounted upon a shaft which is preferably supported in one or more bearings 19 at one side only so as to facilitate removal of the basic ring blanks. The presser roller 16 located on the inside of the ring blank while it is being formed is preferably smaller than the associated or outer presser roller 17 which may be power driven while the inner roller is not.

In addition to the foregoing, means are provided for cutting the flattened wire into predetermined lengths suitable for forming a basic ring blank of the desired size. Such cutting means may consist of an oscillatable shear member or the like 21 of any suitable form and means for automatically actuating the shear after a predetermined length of wire has been fed beyond the presser rollers. For this purpose any suitable operative connections 22 may extend between the oscillatable shear member and the driving mechanism 23 of the presser rollers.

It will be appreciated that the invention is necessarily not restricted to the production of circular rings as aforesaid, but that it may be readily adapted to produce noncircular rings such as cam formed piston rings if so desired by substituting appropriately shaped pressing tools.

Various other modifications, alterations and/or additions may be introduced into the foregoing without departing from the ambit of the invention as defined by the appended claims.

Having now described our invention, what we cl aim as new and desire to secure by Letters Patent is:

1. A method of forming a metal ring blank from stock of circular cross section which comprises cold pressing the stock so as to change its original circular cross-sectional shape into a substantially cross-sectional barrellike formation defined by opposite flat surfaces and intervening convex surfaces, curving said stock into substantially ringlike formation with said flat surfaces defining radially inner and outer surfaces, respectively, of the ring blank so formed, and subsequently locating the ring blank of barrellike cross section in a chamber of predetermined shape in cross section and subjecting said ring blank while so located to a second cold pressing operation so as to cause axial compression thereof, whereby molecule flow within the ring blank during such second pressing operation is facilitated until substantially all of the metal in said blank has passed its yield point and set, without the pressed blank filling said chamber.

2. A method according to claim I, wherein the first pressing operation designed to flatten the original circular bar stock is carried out at the same time as the flattened stock is being curved into the desired shape.

3. A method according to claim I wherein a sizing mandrel is inserted into said ring blank to engage the radially inner surface thereof prior to said second pressing operation, and said mandrel defines one wall of said chamber.

4. A method according to claim 1 wherein a sizing ring is located about said ring blank so as to engage the radially outer surface thereof prior to said second pressing operation, and said sizing ring defines one wall of said chamber.

5. A method according to claim I wherein, during said second pressing operation, the radially inner and outer surfaces of said ring blank are held to predetermined respective diameters by opposed surfaces of said chamber.

6. Apparatus for forming a metal ring blank of the kind indicated from stock of circular form in cross section, said apparatus comprising a pair of opposed presser rollers, drive means operatively connected to at least one of said rollers, to

cause rotation thereof, directing means for directing the leading end of the wire stock between said presser rollers whereby the wire stock is flattened by said rollers so as to have two oppositely directed flat surfaces, guide means located at that side of the presser rollers remote from said directing means and arranged to guide the leading end of the flattened wire stock as it emerges from between said rollers into a curved path of predetermined diameter, whereby said flat surfaces define the radially inner and outer surfaces respectively of the section of wire stock disposed in said curved path, severing means for separating the curved section of flattened wire stock from the succeeding body of said wire stock, locating means for receiving said severed curved section of wire stock and holding the same against substantial radial movement, and a pair of opposed platens operative for engaging opposite axial end surfaces of said curved section of stock while on said locating means so as to axially compress said curved section.

7. Apparatus according to claim 6 wherein said severing means includes an oscillatable shear member and means for automatically actuating the shear member after a predetermined length of wire stock has been fed beyond said presser rollers.

8. Apparatus according to claim 6 wherein said locating means includes a sizing mandrel for receiving said severed curved section of wire stock so as to engage the radially inner surface thereof, and said pair of opposed platens are operative for engaging opposite axial end surfaces of said curved section of stock to axially compress said curved section.

9. Apparatus according to claim 8 wherein one of said platens is provided with a shoulder defining a cylindrical surface which surrounds the radially outer surfaceof said curved section of stock so as to limit radially outward expansion of the said curved section during axial compression thereof.

10. Apparatus according to claim 6 wherein said locating means includes a sizing ring for location about said severed curved section of wire stock so as to engage the radially outer surface thereof, and said pair of opposed platens are operative for engaging opposite axial end surfaces of said curved section of stock located within said sizing ring so as to axially compress said curved section.

11. Apparatus according to claim 10 wherein one of said platens is provided with a shoulder defining a cylindrical surface which is locatable within said curved section of stock so as'to limit radially inward expansion of said curved section during axial compression thereof. 

1. A method of forming a metal ring blank from stock of circular cross section which comprises cold pressing thE stock so as to change its original circular cross-sectional shape into a substantially cross-sectional barrellike formation defined by opposite flat surfaces and intervening convex surfaces, curving said stock into substantially ringlike formation with said flat surfaces defining radially inner and outer surfaces, respectively, of the ring blank so formed, and subsequently locating the ring blank of barrellike cross section in a chamber of predetermined shape in cross section and subjecting said ring blank while so located to a second cold pressing operation so as to cause axial compression thereof, whereby molecule flow within the ring blank during such second pressing operation is facilitated until substantially all of the metal in said blank has passed its yield point and set, without the pressed blank filling said chamber.
 2. A method according to claim 1, wherein the first pressing operation designed to flatten the original circular bar stock is carried out at the same time as the flattened stock is being curved into the desired shape.
 3. A method according to claim 1 wherein a sizing mandrel is inserted into said ring blank to engage the radially inner surface thereof prior to said second pressing operation, and said mandrel defines one wall of said chamber.
 4. A method according to claim 1 wherein a sizing ring is located about said ring blank so as to engage the radially outer surface thereof prior to said second pressing operation, and said sizing ring defines one wall of said chamber.
 5. A method according to claim 1 wherein, during said second pressing operation, the radially inner and outer surfaces of said ring blank are held to predetermined respective diameters by opposed surfaces of said chamber.
 6. Apparatus for forming a metal ring blank of the kind indicated from stock of circular form in cross section, said apparatus comprising a pair of opposed presser rollers, drive means operatively connected to at least one of said rollers, to cause rotation thereof, directing means for directing the leading end of the wire stock between said presser rollers whereby the wire stock is flattened by said rollers so as to have two oppositely directed flat surfaces, guide means located at that side of the presser rollers remote from said directing means and arranged to guide the leading end of the flattened wire stock as it emerges from between said rollers into a curved path of predetermined diameter, whereby said flat surfaces define the radially inner and outer surfaces respectively of the section of wire stock disposed in said curved path, severing means for separating the curved section of flattened wire stock from the succeeding body of said wire stock, locating means for receiving said severed curved section of wire stock and holding the same against substantial radial movement, and a pair of opposed platens operative for engaging opposite axial end surfaces of said curved section of stock while on said locating means so as to axially compress said curved section.
 7. Apparatus according to claim 6 wherein said severing means includes an oscillatable shear member and means for automatically actuating the shear member after a predetermined length of wire stock has been fed beyond said presser rollers.
 8. Apparatus according to claim 6 wherein said locating means includes a sizing mandrel for receiving said severed curved section of wire stock so as to engage the radially inner surface thereof, and said pair of opposed platens are operative for engaging opposite axial end surfaces of said curved section of stock to axially compress said curved section.
 9. Apparatus according to claim 8 wherein one of said platens is provided with a shoulder defining a cylindrical surface which surrounds the radially outer surface of said curved section of stock so as to limit radially outward expansion of the said curved section during axial compression thereof.
 10. Apparatus according to claim 6 wherein said locating means includes a sizing ring for locatiOn about said severed curved section of wire stock so as to engage the radially outer surface thereof, and said pair of opposed platens are operative for engaging opposite axial end surfaces of said curved section of stock located within said sizing ring so as to axially compress said curved section.
 11. Apparatus according to claim 10 wherein one of said platens is provided with a shoulder defining a cylindrical surface which is locatable within said curved section of stock so as to limit radially inward expansion of said curved section during axial compression thereof. 